For restraining vibrations caused due to a pressure within a cylinder (which will hereinafter simply be referred to as an in-cylinder pressure) when an internal combustion engine stops, there has hitherto been known a technology (refer to, e.g., Japanese Patent Application Laid-Open Publication No. 2000-257458) of decreasing the in-cylinder pressure by reducing an air quantity in the cylinder in advance of a stop of the internal combustion engine.
On the other hand, if the in-cylinder pressure is lowered when the internal combustion engine stops, a crank angle when the internal combustion engine stops gets easy to scatter. If there occurs the scatter in the crank angle when the internal combustion engine stops, it follows that there must be a scatter in position of a piston in the cylinder when restarting the internal combustion engine. As a result, there also must be scatters in time and in energy expended for restarting the internal combustion engine, and this leads to deterioration in drivability and in fuel consumption when restarting the internal combustion engine.
Such being the case, there is known a technology (refer to, e.g., Japanese Patent Application Laid-Open Publication No. 2001-173473) of raising, conversely to the former case, the in-cylinder pressure by increasing the air quantity in the cylinder in advance of stopping the internal combustion engine in order to restrain the scatter in the crank angle when the internal combustion engine stops. If the in-cylinder pressure rises when the internal combustion engine stops as described above, however, the vibrations of the internal combustion engine is liable to increase.
Further, for example, Japanese Patent Application Laid-Open Publication No. 9-14017 and Japanese Patent Application Laid-Open Publication No. 8-193531 are exemplified as the prior arts of the present invention.